Do aliens exist?
There are few questions of more profound
importance when it comes to our place in
the universe. But while the majority of
people believe alien life is out there,
it's a lot harder to pinpoint exactly
where. At least that was the case until
we started looking at the Trappist one
star system. In the hunt for alien life,
there are few better candidates. We know
that Earthlike planets are fertile
ground for life. After all, life arose
here. So, to find a planetary system
that is seemingly full of Earthlike
planets and is relatively close by, it's
no wonder that scientists are
interested.
Those researchers have now turned
humanity's most powerful space telescope
on the Trappist one system. So, it's
time to find out the truth. Has Web
confirmed that the planets of the
Trappist One system are conducive to
life or is it back to the drawing board?
I'm Alex Mccoan and you're watching
Astramm. And together in this supercut,
we will go through every planet in the
Trappist system and see why new data is
narrowing down the most likely places
life could arise.
Evaluating a star system for
compatibility with life is tricky.
Although much of it is about the planets
themselves, a large portion of the
conditions depend on the star they're
orbiting. So, let's begin at the heart
of the Trappist system, Trappist one
itself. The ultra cool red dwarf star, a
star which is just a little bit bigger
than Jupiter, but a lot more massive.
Red dwarf stars are the most common type
of star in the galaxy. Even our closest
neighbor, Proxima Centauri, is a red
dwarf, as are 50 of the closest 60 stars
to us. Being so cool means they are very
longived. Stella models suggest they
could exist for trillions of years,
which is far more than the current age
of the universe. Although there are many
known red dwarfs with exoplanets around
them, typically red dwarfs are dubious
candidates to have life. This is because
the Goldilock zone or the distance from
the star where water could theoretically
pull on the planet's surface is
extremely close to the parent star.
Meaning any exoplanets orbiting in this
zone are likely tidily locked. This
means one side to the planet would
always be facing the star and the other
side would be in perpetual night and the
night side would be cold enough for
gases in the atmosphere to freeze. Also,
red dwarf stars are often flare stars or
stars that can have their brightness
increase very rapidly to magnitudes
brighter than they are normally. This is
similar in a way to a solar flare on our
sun, but on a much grander scale. This
variation in temperatures and radiation
is not good for life to develop on any
planets nearby or for planets retaining
their atmospheres during a huge flare.
Travis 1, however, while being a red
dwarf, does not flare up as much as its
other red dwarf cousins. 30 times less
than a typical red dwarf star. Great for
the chances that atmospheres exist on
the exoplanets around the star.
Although the star was first discovered
in 1999, its full planetary lineup
wasn't revealed until 2017 when it
became the first and only planetary
system to be discovered by the Trappist
optical robotic telescope. This
telescope is made up of two parts.
Trappist South in the Chilean Mountains
and Trappist North in Morocco's Atlas
Mountains. They use transit photometry,
a technique that measures periodic
changes in the brightness of a star to
find orbiting planets. In other words,
if a planet passes between us and the
star, then some of its light is blocked,
and so we detect a dip in the stars
apparent output. By taking multiple
observations, the telescopes were able
to isolate the individual orbits of
multiple planets around Trappist 1.
Initially, their data analysis only
found the three innermost planets, but
further data from both of the Trappist
telescopes as well as the Spitzer
Infrared Space Telescope took this total
to seven. And not only that, but they
are all rocky and all, at least roughly
Earth-sized, making this the most
Earthlike planets found around any star.
But with such a small dim star at the
center, is there really any hope that
they could be habitable?
Let's now talk about the planets of
Trappist one. It should be noted that
our current observations aren't going to
be perfect and will only improve as time
goes on, but this is what we think at
this point in time.
Optimistically speaking, six of the
seven planets within Trappist 1 orbit
within the systems Goldilock zone. These
planets are so close together, the
furthest out planet still only orbits at
roughly 9 million km away from the star.
In comparison, Mercury orbits our star
at 58 million km.
Trappist 1b is the closest planet to the
star and it orbits its star quickly. A
year on Trappist 1b lasts only 36 hours.
It's slightly larger than Earth, but
with the same mass, meaning surface
gravity would be about 80% of Earth's,
quite similar to Venus. It was initially
thought that like Venus, it also had an
extremely thick atmosphere, potentially
full of CO2, meaning that because this
planet only orbits 1.7 million km from
the star, it would have been really hot.
However, new data from the James Webb
Space Telescope might have revised our
opinions. The James Webb Space Telescope
is one of the most powerful and
sensitive telescopes to date, and the
teams who were involved with developing
the telescope were rewarded with
guaranteed observation time. One group,
the deep reconnaissance of exoplanet
atmospheres through multi-instrument
spectroscopy. That's right, the Dreams
team immediately wanted to set James
Webb sights on the Trappist One system.
The James Webb Space Telescope is
uniquely sensitive and precise. So much
so that it can detect spectral
signatures from the thin band of gas
that makes up the atmospheres of these
planets a whole 40 lighty years from our
own. It does this thanks to a technique
called transmission spectroscopy.
As an exoplanet passes its mother star,
James Web not only measures the drop in
brightness but also how the spectrum of
light changes. The telescope's near
infrared spectrometer or nearspec for
short measures the wavelengths of
infrared radiation closest to the
visible spectrum. Molecular bonds absorb
energy in this range and different bonds
like this carbon hydrogen bond in
methane or this carbon oxygen double
bond in carbon dioxide absorb different
wavelengths. It means that by measuring
which wavelengths are absorbed as a
planet transits its star, we can first
of all work out if there is an
atmosphere and then if so, determine
which gases are present.
And it's been particularly easy to get a
read at Trappist 1. In fact, the data we
have is 10 times more sensitive than
what we have on any other system. Why?
Counterintuitively, it's because the
star is relatively dim. The light a
planet obscures causes a bigger relative
drop in apparent brightness of this star
than the same planet passing in front of
a large bright star. A bigger difference
is easier to measure.
With the help of the web data, spotting
atmospheres in the Trappist one system
felt less like a slog and more like a
game with scientists spending time every
day trying to crack the code on which
planets could be habitable. And I bet
they had fun with it. But if you're
Speaking of seeing, let's go back to what the web saw on Trappist 1B.
Thanks to the James Web Space Telescope,
it has been revealed that Trappist 1b is
much cooler than it had been predicted.
surface temperatures on its sunward side
only reached 227° C, which essentially
rules out any significant atmosphere.
There is no chance of life on this bare
rock. But what of the other planets?
Trappist 1C is the next planet orbiting
at 2.4 million km away from the star.
Its year lasts 58 hours. At this
distance out, it is getting about two
times the starlight Earth gets from our
sun. Its size and mass are about 10%
more than Earth, which means it has a
very similar gravity to Earth. It is
very similar to Trappist 1b in that
scientists initially believed it to also
have a thick water vapor atmosphere.
However, once again, the James Web Space
Telescope revealed a much cooler surface
temperature than expected.
Interestingly, the coolest rocky
exoplanet ever categorized based on
thermal readings. This means that once
again, there is either no atmosphere on
Trappist 1C or a carbon dioxide
atmosphere that's even thinner than the
one on Mars with no clouds. So, it's
likely that Trappist 1C was formed with
little water as otherwise some might
have become water vapor in the
atmosphere at these temperatures and
scientists don't see any.
Next is Trappist 1D. Only an extra 1
million km further out than Trappist 1C.
1 year lasts only 97 hours. Trappist 1D
is kind of like a mix between Earth and
Mars as it is 30% smaller than Earth and
only 30% as massive, meaning the surface
gravity is little under half of Earth's.
It is found on the inner part of the
Goldilock zone, meaning at this point in
the star system, the surface temperature
is now cool enough for water to pull on
the surface. It only receives 4.3% more
starlight than Earth. And combine this
with stellar flares from the star. It is
likely to still be pretty toasty for our
standards. According to the James Web
Space Telescope data, Trappis 1D does
not have an Earthlike atmosphere. No
water, methane, or carbon dioxide have
so far been detected. But this does not
rule all possible atmospheres out. There
are some indications that Trappist 1D
could have a volatile layer on the
surface. Perhaps an ocean hidden beneath
a thick, obscuring atmosphere that could
be throwing off Web's readings. And this
is where oceans and atmospheres become
very important because as I mentioned
all these planets are tidily locked.
Meaning a thin atmosphere or no
atmosphere means that one side of the
planet could be scorched and the other
side would be freezing much like what
happens with Mercury. Venus on the other
hand has a thick atmosphere which
circulates the heat around the planet
meaning day or night the temperature is
the same. So if Trappist 1d has only a
thin atmosphere or small ocean, the
chances are that one side of the planet
would be devoid of anything but rock.
The other side might be covered in ices.
There might be a small band of
habitability along the twilight zone,
but that would be it. With a large ocean
or atmosphere, the planet might be able
to distribute the heat much better,
meaning it could be habitable all over.
As much as we understand habitability
anyway, this planet may well be an ocean
world with over 250 times the amount of
water, more than Earth's oceans,
although other studies have suggested
the atmosphere could be more similar to
Venus's. Conversely, there could be no
atmosphere there at all. The JWST has
not been able to rule this one out
either way. Next, let's take a look at
Trappist 1F.
From Trappist 1 F and beyond, we are
still in the Goldilock zone, but it is
starting to get much cooler at this
distance. Trappist 1F orbits a distance
of 5.8 million km from the star and a
year takes 220 hours or roughly 9 days.
Its size is very Earthlike, although it
is less dense, meaning surface gravity
would be about 80% of Earth's. The most
recent studies on this planet have
suggested that its low density means it
is likely to be 20% water which at this
distance from the star would cause a
massive greenhouse effect meaning the
water would be in gaseous form. This is
known as a steam world and would
probably be no more habitable than the
ice or gas giants of our solar system
due to the high pressure and temperature
on the surface likely in the hundreds of
degrees.
Trappis 1g is slightly bigger than Earth
and orbits at 7 million km, taking 12
days to do so. There hasn't been too
much information discovered about this
planet other than water has again been
found on it. This planet is still found
in the Goldilock zone, although right on
the far edge. So, it is still a
candidate for habitability.
And lastly, Trappist 1H. It orbits at
9.3 million km and takes 19 days to do
so. It's the smallest of the known
exoplanets in the system and also the
least dense, meaning it gravity is
comparable to our moons. Due to the cool
nature of the host star, being this far
out means the planet is likely icy as it
does have water. Theoretically, it could
also have liquid water on the surface if
it had a hydrogen-rich atmosphere to act
as a greenhouse gas. But again, little
is known about this planet. So, we've
reached the edge of the Trappist one
system. Could this system really be
habitable? Well, it depends on a number
of factors. But while some of these
exoplanet candidates are unlikely,
others so far remain promising. Water
has been detected on some. The host star
is a red dwarf, but not a very active
one. If these exoplanets have strong
enough magnetic fields, they could
deflect a lot of the solar wind. They
are also all roughly Earth-sized with
similar gravities and densities. Not a
huge factor for life, but we know it
worked here. And lastly, although these
planets are tightly locked, they may
still have mechanisms for evenly
distributing the heat across the planet.
But you might have noticed earlier that
I missed a letter. I went straight from
Trappist 1D to F. That is because I
saved our best candidate for a
life-supporting planet until last.
Trappist 1E.
Trappis 1E orbits only 113th of
Mercury's orbit which means it orbital
distance is right in the middle of the
predicted habitable zone where it
receives about 2/3 of the energy that we
do from our sun and that is why
scientists are so curious about this
planet using James web space telescope
measurements the team have already
discounted Trappis 1 C and D from having
atmospheres but the results from
observations of Trappis 1E a rocky
planet around 0.9 times the size of
Earth was so intriguing the scientists
couldn't ignore them. It looked like
this planet may in fact have an
atmosphere and that was more than enough
evidence for the Dreams team to decide
to use up all their guaranteed James
Webb time trying to find more.
So far they've seen four Trappist 1e
transits with James Webb. But what did
they find?
Well, we can start by discounting a few
possibilities. We now know that Trappist
1E does not have a primordial
atmosphere, one a planet is born with.
These are usually dominated by light
gases like helium and hydrogen, which
haven't been detected. They were likely
stripped away by the stars radiation
early on in its life. nor does it seem
to have a carbon dioxide dominant
atmosphere like Venus, which is thick
and dense. An atmosphere like that of
Mars, which is thin and sparse, is also
unlikely given the recent measurements.
Believe it or not, all of this is good
news, as it's unlikely that any of these
atmospheres could support life. Well,
not as we know it anyway. So, what
atmosphere does it have?
Well, here's the big one. There could be
an Earthlike atmosphere, one dominated
by a heavier gas such as nitrogen, with
a strong greenhouse effect from water,
carbon dioxide, or methane. Such an
atmosphere with a surface pressure of
around one bar, equivalent to Earth's,
may be able to sustain enough heat
transfer to the dark side of the planet
to allow a global surface ocean despite
it being tidily locked.
Were this confirmed, that would make
headlines the world over.
However, that might be too much to ask.
The data instead slightly favors the
idea that Trappist 1e is a cold planet
without a global ocean.
Instead, high levels of methane could be
creating a reverse greenhouse effect.
Trappist 1 has a surface temperature of
about 2,300°,
much cooler than our sun's 5,500°,
and more of the energy it outputs is
shifted to the near infrared
wavelengths. Atmospheric methane can
absorb that energy before it even
reaches the surface of the planet, then
remit it into space, resulting in a
cooler atmosphere. For the tidily locked
Trappist 1E, this would mean that liquid
water may only exist on the surface of
the planet that permanently faces the
star. No global ocean here. But that's
not necessarily bad news for life
either. Such conditions could satisfy
Darwin's warm little pond hypothesis of
the origin of life. And atmospheric
modeling has backed this up. Simulation
suggests that even if Trappist 1e has
limited water, or if what water there is
is locked on the dark side of the
planet, it could still have a stable
atmosphere. Although this may lead to
what's known as Terminator habitability,
where life could only find a home across
a dynamic band in perpetual twilight
that separates day from night. But water
on the surface isn't the only option. We
know Trappist 1e is rocky, but not much
more than that. It may be an icy
volcanic planet with a subsurface ocean
like we find on Europa and Enceladus in
our own solar system. Life on Earth is
believed by some to have formed near
deep sea vents and the same process
could happen on 1E.
No matter where on Trappist 1E water may
be, life is possible. There's an energy
source and potentially an atmosphere
that provides the building blocks for
life. But there is one issue. Although
all these things are possible,
scientists can't completely rule out the
possibility that Trappist 1e is a cold,
barren, and airless marble with no
atmosphere at all. So, we need to talk
about what could prevent a stable
atmosphere from ever forming. And in
this case, it's the red dwarf star
Trappist 1 itself. I know I said earlier
that Trappist 1 was not as bad as other
red dwarf stars, but that's not a high
bar. Let's take a closer look at this
star.
Imagine standing with me on Trappist 1E
just for a second. Look up. The star
above us would appear more than four
times as large as our sun in the sky.
The star would be a deep red orange
color illuminating the sky as if it were
in perpetual sunset. What a sight that
would be. Now, as I said, red dwarfs are
extremely active and they produce more
powerful flares than our sun and more
often, too. The worst recorded
geomagnetic storm to ever hit Earth was
the Carrington event in 1859, a greater
than 1 in 100year event. Trappist 1 is
believed to release a flare this
powerful more than once every 2 days.
You'd likely be able to watch solar
flares arcing out into space in real
time. And they carry huge amounts of
energy towards a planet enough that over
time any atmosphere could be stripped
away, making life as we know it all but
impossible. That's assuming that the
atmosphere was ever allowed to form at
all. As mentioned, red dwarfs are
stupendously longived. Trappist one is
expected to exist for 10 trillion more
years. That is 700 times the current age
of the universe. By comparison, our sun
likely only has 5 billion years left
before it becomes a red giant.
You might think given the stability and
lifespan of a red dwarf, there would be
plenty of time for life to find a way.
But because of their long lives, their
chaotic and energetic teenage years
before red dwarf stars settle down are
correspondingly longer. It's during
these formative years that some planets
begin to produce their own atmosphere,
slowly replacing their primordial
hydrogen helium atmosphere with one
comprised of heavier molecular gases
such as carbon dioxide, nitrogen, and
methane. These chemicals are released
from inside the planet through volcanic
activity. The problem is if the
aggressive atmosphere stripping phase of
a star lasts too long, then an
Earth-sized planet might not have enough
resources within its interior to fully
generate a stable lifeupporting
secondary atmosphere.
The unfortunate reality is that if a
planet's atmosphere isn't established
before 5 billion years, it may never
generate one, condemning the planet to a
death sentence before it was ever
allowed to live.
I know it's actually sounding rather
hopeless for Trappist 1e, and I bet
you're wondering, how is this one of the
most promising planets? But we don't yet
know one way or the other whether an
atmosphere has survived or not. We've
already seen there are hints of its
existence. And although the stars
violent outbursts may be one ease
downfall, they may also be completely
necessary for life to begin. UV
radiation from flares may be essential
to create RNA building blocks, molecules
that are central to the metabolism of
every life form ever found. And now that
Trappist 1 is in its calmer main
sequence phase with lower UV and X-ray
radiation than in its juvenile past,
there is a chance of a stable habitable
atmosphere existing on Trappist 1e. And
that atmosphere could have protection
from the continuing flares with its own
magnetic field just like the Earth does.
The Earth's magnetic field exists
because its outer core is a moving mass
of molten iron and nickel. There is a
good chance that Trappist 1E has a
similar system. In fact, Trappist 1's
close orbit to the red dwarf could
actually help maintain its magnetic
field. If Trappist 1's orbit is
eccentric, this would cause repeated
compression and relaxation of the planet
shape. This process creates internal
friction that could heat the interior as
much as 0.18 W per meter squared. That's
roughly 24 times the tidal heating flux
generated in the earth. We see a similar
process in Jupiter's moon Io. Io is
tidily locked with an eccentric orbit
and gets stretched and squashed by the
gravitational interactions with the
other Jovian moons pumping it full of
energy and making it the most
volcanically active body in the solar
system.
So where does this leave us? Well, we
may have an Earth-sized volcanically
active rocky planet with the building
blocks for life, its own atmosphere and
magnetic field, orbiting in the
habitable zone of a relatively calm red
dwarf, or it could be a cold, dead
world.
So, let us know in the comments which
you think will eventually be confirmed.
We might not get an answer until the
proposed Habitable Worlds Observatory, a
telescope designed to look for life
around stars like our own, which
launches in 2041.
But until then, James Webb's
observations are our best bet. The fact
we are able to measure the light
absorbed by a thin gaseous layer around
a rocky planet orbiting a dim red dwarf
star 40 lighty years away is pretty
incredible. And scientists haven't given
up hope. They've learned from the first
sets of James Web data and modified
their technique to achieve more precise
measurements. And as they examine the
results of more web data, they hope to
be able to confirm the presence or
absence of carbon dioxide and a
secondary atmosphere, a key step in the
search for life on one E. No joy on that
front yet, though. The most recent study
on the topic tentatively suggests that
Trappist 1e might have a methane
atmosphere, but this might also be
interference from its host star. Methane
in Trappist 1 itself getting in the way
of the smaller planet. Perhaps Trappist
1E and its neighbors will turn out to
have a unique inhospitable atmosphere.
Or perhaps one that could theoretically
support life. Or maybe, just maybe,
we'll find one just like home. It's
exciting to find so much potential for
life relatively nearby, even in the
midst of an extreme environment. But
whatever the atmosphere turns out to be
on Trappist 1e. With the recent
discovery of formations on Mars that are
thought to have been impossible to form
without life, I find it hard to shake
the feeling that the discovery of
extraterrestrial life feels inevitable.
The only question is when.
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